Field of the Invention
The present invention is directed to the preparation of a novel class of membranes comprising a polymer containing a polyamideamine functional group of the formula: ##EQU1## WHEREIN: X is selected from the group consisting of R.sub.1, ##EQU2## Y is selected from the group consisting of R.sub.7, ##EQU3## wherein: R.sub.1, R.sub.2, R.sub.3, R .sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.9, R.sub.11 and R.sub.12 are organic diradicals independently selected from the group consisting of alkylene, cyclic alkylene, phenylene, phenyl dialkylene, bisphenylene alkylene and substituted diradicals thereof wherein the substituents are selected from the group consisting of oxygen, sulfur and nitrogen; and wherein R.sub.4 and R.sub.10 are organic radicals selected from the group consisting of alkyl, cyclic alkyl and phenyl;
WITH THE PROVISO THAT AT LEAST ONE OF X and Y as defined above contains a tertiary amine group; and wherein:
N IS AN INTEGER DESIGNATING THE REPEATING MONOMERIC UNITS OF THE POLYMER.
The novel membrane compositions herein can be produced as asymmetric membranes by solution casting; or more significantly, homogeneous high performance, symmetric membranes may be produced using melt processing techniques.
Moreover, we have found that by incorporating a compatible additive or compatible high molecular weight matrix polymer with the polyamideamine, durable, chemically resistant membranes can be produced having controllable hydrophilicity and porosity.
The membranes formed using the systems of the present invention may be adapted for use in such applications as solvent extraction, dialysis, reverse osmosis, ultrafiltration, gas-liquid absorption, pervaporation, gas-gas separation, etc.
The membranes of the invention are particularly useful in the form of hollow fibers, flat sheets or tubes in the solvent extraction process described in our copending application Ser. No. 320,341, filed Jan. 2, 1973.
In the membrane solvent extraction process disclosed in that application, two substantially immiscible liquids, B and C, are separated by a membrane so there is no phase-to-phase contact between the two liquids. During the extraction, the solute A, dissolved in liquid B, diffuses from the liquid B into and across the membrane and ultimately passes into the liquid C. Hollow fiber membranes are advantageously employed in this process since they provide a large mass transfer area per unit volume as the mechanism for selectively extracting the solute from one liquid medium and depositing it into a second liquid medium without requiring direct contact between the two media. For use in such two-phase extraction systems, the membrane must possess a high degree of diffusivity, i.e., preferably about 10.sup..sup.-7 to 10.sup..sup.-6 cm.sup.2 /sec, it must permit to bulk-solution diffusion, and be chemically stable to solvents or acid or basic mediums.